Project Summary This purpose of this project is to describe secondhand electronic cigarette aerosol exposure and associated markers of lung function in children who reside with daily vapers. E-cigarettes vaporize liquids typically containing nicotine, propylene glycol (PG), vegetable glycerin (VG), and various flavorings inhaled and exhaled by the user. Harmful chemicals such as aromatic volatile organic compounds (VOCs), trace metals, and tobacco-specific nitrosamines have also been reported in mainstream and secondhand e-cigarette aerosols. All of these chemicals have known adverse health effects, including effects on the respiratory system. With the rapid increase in e-cigarette use, particularly among those of child-bearing age, secondhand exposure to e- cigarette aerosol is an emerging public health concern. The health effects of secondhand e-cigarette aerosol exposure on the bystander, particularly for children, is not clear. We propose to utilize a case-control design and will recruit 60 children between the ages of 6-12 years (30 cases/30 controls). Our hypothesis is that nicotine and aromatic VOCs associated with secondhand e-cigarette aerosol exposure will associate with alterations in metabolic profiles and metabolic pathways. Further, exposure to these chemicals and metabolic profile alterations will associate with evidence of impaired lung function. Using silicone wristband passive air sampling devices and salivary metabolomics analysis, we will: 1. Examine associations between secondhand e-cigarette aerosol chemical exposures (nicotine, benzene, and toluene) and salivary metabolic profiles and pathways. 2. Examine associations of secondhand e-cigarette chemical exposure and salivary metabolic profiles with markers of lung function (fractional exhaled nitric oxide, forced expiratory volume in one second, forced vital capacity, mid-expiration forced expiratory flow rate, and parent-report of recurrent/chronic respiratory symptoms). The proposed project will supplement the HERCULES Exposome Center (P30ES019776) and aligns well with the overall Center's mission to provide a more comprehensive assessment of environmental influences using exposome-based concepts and approaches including metabolomics. To our knowledge, this would be the first study to examine the impact of secondhand e-cigarette aerosol exposure on pediatric lung function.